Mr. Keen, Tracer of Lost Persons

June 11, 1940 to June 25, 1954

550 episodes known to exist

Mr. Keen, Tracer of Lost Persons was one of radio's longest running shows, airing (October 12, 1937 to April 19, 1955), continuing well into the television era. It was produced by Frank and Anne Hummert. The sponsors included Whitehall Pharmacal (as in Anacin, Kolynos Toothpaste, BiSoDol antacid mints, Hill's cold tablets and Heet liniment), Dentyne, Aerowax, RCA Victor and Chesterfield cigarettes. It aired on the NBC Blue network until 1947, when it switched to CBS.
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Runs

Radio series often ran for multiple seasons and/or through many incarnations with different radio networks, sponsors, cast/crew, and revivals after many years.